This invention relates generally to a filter for the exhaust of a two-stroke gasoline engine, and more particularly, to a porous ceramic filter in such an exhaust.
Two-stroke engines are popular power generation sources for certain applications, including personal transportation vehicles, such as motorcycles, scooters, and mopeds, small boats, and gas-powered tools and implements, such as string trimmers, leaf blowers, and chainsaws. Two-stroke engines are specifically adaptable to these applications since they have a number of specific advantages over conventional four-stroke gasoline engines. Two-stroke engines have an increased specific power output, since there is a power stroke for each revolution, as opposed to one power stroke for every other revolution in a four-stroke engine. Two-stroke engines are inherently lighter and less complex, and thus cheaper to manufacture and operate, since they typically have no camshaft and associated valves. The high specific power and light weight contribute to an increased power-to-weight ratio over four-stroke engines. Further, two-stroke engines can operate in nearly any orientation, since lubrication of the moving parts is provided by a fuel and oil mixture, instead of an oil sump.
Two-stroke engines, however, are known as notorious contributors to air pollution, and for their noxious exhaust emissions. The increased levels of pollution arise from the combustion of oil lubricants that are mixed with the fuel, and due to the inefficiency of the incoming air, fuel, and oil charge that scavenge the exhaust from the combustion chamber. The down stroke of the piston in a two-stroke engine compresses the crankcase chamber driving the air/fuel charge into the combustion chamber, displacing the burned fuel byproducts. Some of the unburned fuel and oil mixes with the exhaust as it exits the chamber. Accordingly, increased levels of hydrocarbon particulate, compared to four-stroke engines result.
Exhaust filters and catalytic converters have been installed on two-stroke engines to reduce the degree to which this type of engine contributes to pollution, but the soot and particulate loading of conventional filters and catalytic converters results in decreased effectiveness of the catalyst, and reduced performance due to increased backpressure.
Accordingly, there is a need for an exhaust filter that can be applied to two-stroke engines to capture and reduce particulate emissions, without detracting from the performance and efficiency of these power sources.